The present invention is especially directed to crushing apparatus in which material to be crushed is fed into the nip between the teeth of a pair of power driven counterrotating rolls to be crushed into relatively fine particles.
The present invention is especially directed to an improvement over the crusher roll assembly disclosed and claimed in a commonly owned DeVita and Watkins application Ser. No. 296,897, filed Aug. 27, 1981, and assigned to the assignee of the present application.
As described in the DeVita et al application referred to above, toothed crusher roll assemblies of the type with which the present invention is concerned have had practical limitations in crushing incoming material to particles of the desired fineness in those situations where the incoming material took the form of relatively large sized lumps or portions. Crusher roll systems exemplary of the prior art are those illustrated in patents:
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One specific example with which the present invention is concerned is that of crushing the used sand cores employed in foundry operations, to recover the sand for use in making additional cores. The comparative size of the sand cores and the sand particles is such that the prior art crushing of the cores, or significant portions thereof, had to be accomplished in a two or three step process in which the material was passed through successively finer sets of crusher rolls before the desired particle size could be achieved.
The present invention is especially directed to an improved tooth form which enables a crusher roll assembly to accept relatively large sized pieces of material while being operable to crush this material into relatively fine particles in a single pass through the roll assembly. Whereas previous machinery has normally accomplished 6:1 reduction, the present invention has exceeded 50:1, with 20 inch size material reduced to under 3/8 of an inch.